A hollow roller which can be heated with steam in this way is used, for example, in the production of corrugated board as a so-called fluted roller, as known from U.S. Pat. No. 6,092,579. Furthermore, hollow rollers of this type, which can be heated with steam, are used as so-called preheating rollers in corrugated board systems in order to preheat paper webs. Further areas of use are to be found in other technical areas; hollow rollers of this type are regularly used to warm or heat materials guided over them in webs. In this case, on the one hand, steam, generally saturated steam or superheated steam is blasted into the inner hollow roller. It gives off its heat via the inner wall of the hollow roller to the shell thereof, whereupon the water vapour condenses. The condensate collects because of the gravitational force and the centrifugal force of the rotating hollow roller on the inner wall thereof. This condensate layer acts in an insulating manner and therefore disturbs the heat transfer from the steam onto the roller. To remove the condensate, a siphon pipe is used, the suction opening of which is located close to the inner wall of the hollow roller. The spacing of the suction opening of the siphon pipe from the inner wall of the hollow roller is decisive for the residual quantity of condensate located in the interior of the hollow roller. Moreover, when a siphon pipe rests on the inner wall of the roller shell, the suction opening may cut in, so the siphon pipe rests tightly on the inner wall with the consequence that condensate can no longer be removed by suction.
In a hollow roller of this type, which can be heated with steam, known from EP 0 922 921 B1, the siphon pipe consists of an outer rigid support pipe and a flexible insert pipe displaceably mounted therein, so the spacing of the suction opening from the inner wall of the hollow roller can be adjusted. It has been shown in practice that it is only possible to adjust the spacing of the suction opening from the inner wall of the hollow roller when the hollow roller is stationary, in other words in operating breaks.